Catalytic synthesis of a monodisperse olefin block copolymer using a living polymerization system

Polymerization of norbornene has been conducted with [t-BuNSiMe2(3,6-t-BU(2)Flu)]TiMe2 (1) in toluene at 20 degrees C using modified methylaluminoxane that contained 0.4 mol-% of triisobutylaluminium (TIBA) (dMMAO(0.4)) or 1.8 mol-% of TIBA (dMMAO(1.8)). The 1-dMMAO(0.4) catalytic system undergoes a living polymerization of norbornene. The catalysis of norbornene and propylene with the 1-dMMAO(1.8) catalytic system gives markedly different results because of differences in transfer times of the polymers from Ti to TIBA. The successive addition of norbornene and propylene before the complete consumption of the norbornene in the 1-dMMAO(1.8) system gives monodisperse PNB-block-poly(propylene-ran-norbornene)block-PP terminated with a Ti-PP bond, which is exchanged with TIBA. Hence the repeated addition of the same amount of norbornene and propylene realizes the catalytic synthesis of monodisperse block copolymer in this system.